Hot food storage containers have generally taken the shape of a double walled cylinder with a vacuum or air between the walls. Typically, these containers are first preheated in a stream of hot liquid, i.e. hot tap water, to minimize cooling of the stored food before reaching a container-food temperature equilibrium. Heat is then lost to the environment from both the stored food and the container in relation to the container design and materials of construction. The container is usually designed to resist such heat loss with materials and geometries that passively retain heat.
Similar comments can be made with respect to warming devices that use a plurality of pockets and reflective layers: these "empty" structures passively resist heat loss. Some of the known warming devices are not "empty", however, but are composed of a gel sealed in a soft plastic pouch. Water in the gel can be preheated by conduction, e.g., in warm water, as an active source of heat for the device.
Unfortunately, the integrity of the container seal is crucial to the usefulness of gel containing devices. Leaks and punctures allow the gel to escape thereby rendering the device messy and virtually impossible to repair. Because the gel is difficult to clean from the pouch exterior, sealing tapes cannot be assured of closing off the leak as most adhesives will not bond to the plastic pouch through even a minute layer of residual gel. It is more expedient to discard the leaking pouch than to attempt repairs.
It would be desirable to have an insulation container that could store hot foods for long periods of time without substantial loss of heat.
It would also be desirable to provide a warming device that could be sealed easily in a variety of shapes without substantial mess or repair difficulties if a leak developed.